Method of filling pressure packages with aqueous wax emulsions employing a nitrous oxide propellant



March 22, 1966 M. 515550 3,241,993

METHOD OF FILLING PRESSURE PACKAGES WITH AQUEOUS WAX EMULSIONS EMPLOYING A NITROUS OXIDE PROPELLANT Filed July 23, 1962 INVENTOR.

United States l atent O 3,241,993 METHOD OF FILLING PRESSURE PACKAGES WITH AQUEOUS WAX EMULSIONS EM- PLOYING A NITROUS OXIDE PROPELLANT Louis M. Sesso, Racine, Wis, assiguor to S. C. Johnson &

Son, Inc., Racine, Wis. Filed July 23, 1962, Ser. No. 211,50

9 (Ilaims. (Cl. 106-271) This invention relates to a method for filling pressure packages sometimes referred to as aerosol dispensers. More particularly, the invention relates to a method of filling pressure packages utilizing noncondensable gases.

Two types of propellant are used in the filling of pressure packages, the so-called condensable and noncondensable gases. The words condensable and noncon densable as used in this context are relative terms since all gases liquefy or solidify under extreme conditions of temperature and pressure. These terms are used herein in the manner in which they are commonly used in the pressure packaging industry. Thus, the term condensable gas is used to refer generally to those products which are liquefiable under ordinary temperatures and pressures. Included among the noncondensable gases are nitrous oxide, nitrogen, carbon dioxide and hydrogen. Typical of the condensable gases are the lower molecular weight hydrocarbons, such as isobutane and n-butane, and the fluorocarbons such as trichlorofiuoromethane and dichlorodifiuoromethane commonly known as Propellants 11 and 12 respectively.

The difference in these two types of gas reflect to some extent upon the performance of the products which they are used to dispense.

Condensable gases, frequently referred to as liquefied propellants, are injected into the containers filled with the product to be dispensed in liquefied state. An equilibrium is established between the liquefied phase of the propellant and the gaseous phase of the propellant in the headspace of the container. When the container valve is opened, the gaseous portion of the propellant acts as a piston driving the product to be dispensed downwardly, and up and out through the dip tube. As this occurs, the pressure in the headspace may be temporarily reduced, but if so, it is almost immediately re-established by vaporization of some of the liquefied propellant into the gaseous phase. As long as any propellant remains in the liquefied phase, the pressure in the headspace remains relatively constant thereby driving the product out of the package with constant force when the valve is opened.

In contrast, a product packaged with a noncondensable gas contains propellant principally in the gaseous phase. A limited amount of the noncondensable gas may be soluble in the product phase. The gas is normally injected into the container where it remains in the headspace thereof until the container is emptied of product. As part of the product is emitted from the container, the remainder occupies less space leaving a greater space to be occupied by essentially the same amount of propellant. Thus, the pressure in the headspace diminishes as the product is dispensed, a factor which is taken into consideration when determining the amount of propellant needed. Some of the noncondensable gas which has become solubilized in the product phase will come out of solution and enter the headspace to partially rebuild the 3,241,993 Patented Mar. 22, 1966 ice pressure in the headspace. The extent to which this phenomenon occurs will depend principally on the solubility of the noncondensable gas in the product phase and the existing pressure in the headspace.

As indicated above, two types of propellant have been used in filling pressure packages-the condensable and noncondensable gases. Turning now to filling methods, three distinct procedures have been employed, namely, cold filling, through-the-valve filling, and under-the-cap filling.

Cold filling comprises chilling or refrigerating both the concentrate and the propellant, injecting them into the container while chilled and thereafter inserting and securing the valve assembly and closure in place. This method of filling requires refrigeration equipment and is therefore expensive. Many solutions are adversely affected by refrigeration. Also, water emulsions cannot be refrigerated under 32 F.

In filling through the valve, all of the product ingredients are placed in the container. The valve closure is secured in place and thereafter, the propellant is injected into the container through the valve. A few of the less volatile propellants, such as trichlorofluoromethane, which are commonly used in combination with more volatile propellants, such as dichlorodifluoromethane, may be placed in the container with the product phase, with the more volatile component of the propellant combination injected through the valve. Pressure packaging by filling through the valve does not require refrigeration. However, since the valve passage requirements may be relatively small or the amount of propellant large, con siderable time is required to get the required amount of propellant into the container.

0f the three methods of filling pressurized packages, the under-the-cap method is the latest to become commercially utilized. This method permits the filling of the container with both product and propellant at room temperature with greater speed and economy than is possible using the through-the-valve method. By this method, utilizing filling equipment such as that disclosed in United States Patent 2,947,126, a measured quantity of the active ingredient is first placed in the container. The cap, with valve and operating button attached, is then loosely placed over the top opening of the can after which a closed chambet is formed about and above the container-top opening. The container cap closure including the valve and attached operator button is elevated from engagement with the container top opening, and when this is accomplished, a measured amount of a condensable propellant in liquid form such as dichlorodifiuoromethane is introduced instan taneously into the container through the uncovered open top thereof. The cap, valve and operator button are immediately replaced as an assembled unit and sealed into position, thereby completing the operation.

In summary, pressure packages have been filled by three methods, cold filling, through-the-valve filling and underthe-cap filling. Condensable or liquefiable propellants only, such as isobutane and halogenated hydrocarbons, have been used in the cold filling and the under-the-cap methods, while both condensable and noncondensable gases have been used in the through-the-valve method.

Condensable gases are not without advantages as propellants for pressure packages. However, noncondensable gases possess several advantages over condensable gases. Noncondensable gases are considerably less expensive than condensable gases such as dichlorodifiuoromethane and dichlorotetrafiuoroethane. Noncondensable gases do not liquefy under ordinary temperatures and pressures. Consequently, they may be used to generate a wide variety of pressures without dilution simply by essentially varying the amount of gas compressed in the headspace of a container. A condensable gas, on the other hand, generates a given pressure after liquefication at ambient temperatures which can be modified only by blending it with other liquefied gases or other diluents. Further, a greater product-to-propellant ratio can be established with a noncondensable gas since only a small amount is required to do the job.

With all of their advantages, noncondensable gases possess many disadvantages which have seriously impeded their adoption for use in pressure packaging. Carbon dioxide reacts rapidly with water to form carbonic acid which attacks metal containers leading to serious corrosion and leakage problems and seriously limits its use in anionic emulsion systems. Hydrogen is highly explosive and has been given little consideration as a commercial propellant. Nitrogen exhibits such a low degree of solubility in most liquids that its effectiveness as a propellant is seriously affected after a few initial uses of a product pressurized with it.

It has now been discovered that the noncondensable gas, nitrous oxide, can be very effectively used to pressurize a specialized line of products, namely aqueous wax emulsions, and that pressure packages may be rapidly filled with an aqueous wax emulsion and nitrous oxide by a novel process utilizing the under-the-cap method, thus avoiding the use of refrigeration necessary to the cold filling process and the bottlenecks which accompany filling through-the-valve.

In recent years, pressurized furniture Polishes comprising aqueous wax emulsions have been introduced into commerce. These products contain as surface modifiers Wax or wax and silicone, water, an emulsifying agent and frequently a petroleum distillate such as naphtha. The most useful of these products are very delicately balanced emulsions so that the emulsion breaks when it is sprayed on the surface to be protected. As the emulsion breaks, the surface modifiers are deposited and the water carrier rapidly evaporates or is wiped away with a polishing cloth.

United States Patent No. 2,524,590, issued to Carston F. Boe, discloses a method of spraying an emulsion which comprises initially forming an emulsion comprising two immiscible liquids in emulsified form, the emulsion having water in the continuous phase and a liquefied gas in the dispersed phase.

In describing the propellant systems which may be employed to accomplish this purpose, Boe discloses that oil-sluble hydrocarbons, such as propane or butane or the halogenated derivatives of methane and ethane, after being liquefied may be emulsified directly with a water phase, or they may be dissolved in an oil phase and the resulting solution emulsified with a water phase; or, if desired, they may be first emulsified in a water phase and the resulting emulsion subsequently emulsified in a continuous oil phase. Boe finally states that gases such as carbon dioxide and dimethyl ether, after being liquefied, may be dissolved directly in a water phase and the resulting solution emulsified with an oil phase.

The obvious method of pressurizing an aqueous wax emulsion with nitrous oxide would be to place the product in the container and then inject the nitrous oxide under pressure through the valve stem into the headspace of the container.

It is doubtful that one would grasp from the Boe patent, a method for pressure packaging an aqueous wax emulsion by dissolving nitrous oxide in the water of the emulsion, emulsifying the resultant nitrous oxide water solution with an oil phase in a pressure vessel and finally transferring the resultant oil in water emulsion under pressure to a container from which it is to be dispensed in use. However, even if this procedure were followed in the pressure packaging of aqueous wax emulsions, far from the most desirable result would follow. A pressure vessel for maintaining the complete product including propellant would be required together with the necessary equipment for injecting the total product under pressure into the container from which it is to be sprayed as taught by Boe. As indicated earlier, many aqueous wax emulsions are delicately balanced in order to obtain optimum product performance and tend to break or gel when they are subjected to unusual amounts of agitation as would be the case when the product is subjected to manipulation and transmission under pressure.

All of the difficult problems in the pressure packaging of aqueous wax emulsions may be overcome by the present process which is significantly different from the process of Boe and that outlined above while utilizing the economical and otherwise very desirable condensable gas, nitrous oxide, as the propellant. This is accomplished by dividing all of the ingredients in the product except the propellant, commonly called the concentrate, into two portions, the first portion comprising the surface modifiers, emulsifying agent, petroleum distillate when present, and a part of the water, and the second portion of the concentrate comprising the balance of the water, depositing the first portion of the concentrate into a container, dissolving nitrous oxide in the second portion of the concetrate, thereafter injecting the second portion of the concentrate having nitrous oxide dissolved therein into the container and then sealing the container with a closure comprising a valve assembly through which the product may be emitted under pressure.

The aqueous wax emulsion to be packaged in accordance with the present invention will comprise between about 0.3% and about 10% by weight of a wax and between about 0.3% and about 5% by weight of an emulsifier and between about and about 99.4% by weight of water. When a petroleum distillate is not present preferably the war emulsion will comprise between about 3% and about 6% by weight of wax, between about 0.3% and about 4% by weight of an emulsifier and between about and about 99.4% by weight of Water. The invention possesses its greatest advantages when the aqueous wax emulsion contains a petroleum distillate in the dispersed phase of the emulsion. When a petroleum distillate is present, the emulsion will comprise between about 0.3% and about 12% by weight of wax, between about 0.3% and about 5% by weight of an emulsifier, between about 1% and about 20% by weight of a petroleum distillate, and between about 63% and about 98.4% by weight of water; or preferably when a petroleum distillate is present, the emulsion will comprise between about 0.3% and about 8% by weight of wax, between about 0.3% and about 4% by weight of an emulsifying agent, between about 1% and 15% by weight of petroleum distillate and between about 73% and about 98.4% by weight of water.

When the aqueous wax emulsion to be packaged in accordance with the present invention contains wax, emulsifier, a silicone fiuid and water but no petroleum distillate the emulsion will comprise between about 0.3% and about 6% by weight of wax, between about 0.3% and about 4% by weight of an emulsifier, between about .5% and about 6% by weight of silicone fluid and between about 84% and about 98.9% by weight of Water.

In addition to the above ingredients, a silicone fluid may be advantageously employed in aqueous wax emulsions and such emulsions are particularly profitably packaged in accordance with the present invention. When a silicone fluid and a petroleum distillate are used to form the wax emulsions the emulsion will comprise between about 0.3% and about 3% by weight of wax, between about 0.3% and about 4% by weight of an emulsifier, between about 1% and about 15% by weight of petroleum distillate, between about 0.5% and about 5% by weight of silicone and between about 73% and about 97.9% by weight of water.

The term wax as used herein is intended to include any of the natural and synthetic waxes. Natural Waxes include the animal, mineral, and vegetable waxes. Spermaceti, beeswax, stearic acid and Chinese insect wax are among the animal waxes, while ozocerite, m-ontan, ceresin and parafiin waxes typify the mineral waxes. Vegetable waxes include ca-rnauba, Japan, bayberry and candelilla. Synthetic waxes include long chain polyesters formed by the reaction product of dihydric alcOhOls and dicarboxylic acids terminated with long chain saturated aliphatic alcohols such as the reaction product of tetrahydrophthalic acid, succinic acid and a monohydric saturated aliphatic alcohol having 26 or more carbon atoms. Many other synthetic waxes will be known to those skilled in the art.

Petroleum distillates which may be used in the preparation of the wax emulsion to be used in this invention include naphtha, gasoline, kerosene, benzene, mineral spirits, stodded solvent, mineral seal oil, paraflin oil and the like. Petroleum naphtha is preferred.

Any of the liquid organo polysiloxes, commonly called silicones or silicone fluid may be used in the invention. The preferred polysiloxanes are dimethyl polysiloxane, diethyl polysiloxane and ethyl methyl polysiloxane.

Any of the well-known emulsifying agents such as the monoester of polethylene sorbitan (nonionic), acetic acid salts of n-alkyl amines (cationic), and triethanolamine salts of oleic acid (anionic) may be employed.

As mentioned earlier, the process now presented avoids the use of refrigeration which is costly and cannot readily be used with products containing water. The process is rapid since it is not necessary to pump the nitrous oxide through the valve stem but permits it to be injected rapidly as a water solution by an under-the-cap filling machine. If the nitrous oxide were pumped into the container through the valve after the product concentrate had been placed in the container, an excessive pressure Would have to be initially created in the headspace to compensate for the subsequent solubilizing of a substantial portion of the propellant by the water of the product. For example, it has been determined that a water-based emulsion desired to be packed at 65 p.s.i. gauge with nitrous oxide would require an initial pressure of approximately 110 p.s.i. gauge to compensate for the loss of pressure which occurs when much of the nitrous oxide is dissolved by the water carrier. It is well known that the less pressure a container must withstand the cheaper it may be manufactured, other factors being equal.

The present process is also cheaper for another, but related, reason. In the packaging of pressurized products, the filled containers charged with propellant are submerged in accordance with Interstate Commerce Commission regulations into a tank of water maintained at a temperature of at least 130 F., commonly called a hot tank, as a quality control measure to screen out any containers which may already be defective or which became defective when subjected to the increased pressure developed due to the increased temperature. A product charged with a gaseous propellant must be vigorously shaken for a prolonged period of time before being subjected to this hot tank treatment to effect as complete a solubilization as possible of the propellant in the products liquid carrier. Otherwise pressure would be built up in the containers during the hot tank treatment far beyond that which it is necessary for them to withstand during any reasonably foreseeable conditions of use. Since in practice of the present process, the gaseous propellant is solubilized in a substantial portion of the total product before it is placed in the container, the initial pressure is lower than it would otherwise be and shaking of the filled and charged container is eliminated or greatly reduced.

6 The following examples are presented to illustrate the invention.

Example I A spray wax of the following formula was prepared An aqueous wax emulsion was prepared in accordance with the above formula omitting the nitrous oxide and 68.7% of the specified amount of water. This concentrated' emulsion represented the firs-t portion of the concentrate as the term is used in the present invention. Several 8-ounce cylindrical metal containers were filled, each with 1.75 ounces of this concentrated wax emulsion, using a conventional piston filler, and with 5.25 ounces of water saturated with nitrous oxide using an under-the-cap filling machine of the type disclosed in United States Patent 2,947,126 issued to Focht.

The Water solution of nitrous oxide was prepared and delivered to the under-the-cap filler by use of a system shown in the drawings. This system and its operation will now be described.

Hot and cold water are introduced into conduits 11 and 12 respectively and passes through remote controlled valves 13 and 14, where the rate of passage is regulated by temperature regulator 15. Temperature regulator 15 is suitably connected with conduits 11 and 12 at their junction 18 through a sensitizing element 17 positioned at the junction and connecting means 16, and electrically connected with remote controlled valves 13 and 14 through connections 19 and 20. Temperature regulator 15 responds to the temperature of the Water passing from conduits 11 and 12 past junction 18 and its own setting to adjust remote controlled valves 13 and 14 to maintain the Water at the desired temperature.

Water at controlled temperatures, formed by the mixture of hot and cold water at junction 18, flows through conduit 21 and remote controlled valve 22 into the head space of vacuum deaerating unit 23 where it is dispensed downwardly in a fine spray through spray head 24. Provision is znade for draining conduits 11, 12 and 21 through conduit 25 and valve 26 connected to conduit 21 between junction 18 and remote controlled valve 22. Remote controlled valve 22 is connected electrically through connection 27 to level control unit 28 which in turn is sensually connected through connection 29 and 30 to vacuum deaerating unit 23 at different vertical positions 31 and 32. The input of Water through spray head 24 is regulated by the level control unit 28 and remote controlled valve 22 so that a water level 33 is maintained in the deaerating unit 23 between elevations 31 and 32. The vacuum deaerating unit 23 is equipped with a vacuum gauge 34 and means for draining the vacuum deaerating unit are provided through conduit 35 and valve 36.

The vacuum deaerator 23 is connected at a position above the water level with a vacuum pump, not shown, through vacuum conduit 37. The vacuum deaerator 23 is also connected in parallel at a position below the Water level through conduits 4t), 41, and 42 with feed pumps 43 and 44-. Feed pumps 43 and 44 are in turn connected through conduit 45 with an impregnating tank 46 Whereas deaerated water from the vacuum deaerator 23 is impregnated with nitrous oxide. Conduit 45 is equipped with a pressure relief valve 4-7 and a remote controlled valve 48.

A level control unit 49 similar to level control unit- 30 is connected to the impregnator 46 at positions 50 and 51 through connecting means 52, 53, and 54. The flow of water from the vacuum deaerator 23 through conduit 45 is thus controlled by level control unit 49 and remote controlled valve 48 so that it is dispensed upwardly through spray head 54 at an appropriate rate to maintain the water level 55 between position 50 and 51.

The impregnator 46 is connected through conduit 60 equipped with shut-off valve 61 to vacuum conduit 37 connected with a vacuum generator not shown. This connection permits air to be pulled out of the impregnator prior to introduction of nitrous oxide and water into the impregnator. Mounted in the upper portion of impregnator 46 are a pressure safety valve 62 and a purging means comprising conduit 63 and valve 64.

Below the water level there is mounted in the impregnator 46 a sample tap 65, drain means 66, low level detector 67 and agitating means 63 equipped with a motor 69 and propeller 70 connected by propeller shaft 71.

Nitrous oxide from a supply station not shown enters into top of impregnator 46 under pressure through conduit 72. The pressure under which the non-condensable gas enters the impregnator is controlled by pressure-sensitive element 75 inside the impregnator 46 and to remote control valve 76 through electrical connecting means 77.

Depending upon the type of pressure control unit used at 73, it may be necessary to place a step-down pressure regulator, not shown, in conduit 72. To maintain the water in the impregnator 46 at a desired temperature, a heat exchanger 78 is provided. The heat exchanger 78 is connected to the impregnator below the liquid level through conduit 79 and pumps 80' and 81 connected in parallel by conduits 82 and 83. Water flowing from the impregnator 46 into the heat exchanger 78 re-enters the impregnator above the water level through conduit 84 and spray head 85.

A temperature controlling and recording unit 90 is mounted between the heat exchanger '78 and impregnator 46. Temperature sensitive unit 91 is mounted in the impregnator below the water level and connected to recordcr 99 through connecting means 92. The temperature recorder is also connected with remote control valve 93 through electrical connecting means 92a. Conduit 94 is connected to a cold water supply not shown. Cold water entering heat exchanger 78 through conduit 94 leaves the exchanger through conduit 94a. Conduit 95 connects vacuum deaerator 46 with parallel pumps 96 and 97 which in turn are connected to conduits 98 and 99 through which the water impregnated with nitrous oxide flows toward its intended use. Valves 106 and 101 are connected to the impregnator 46 through conduits 102, 103, and 104 to permit re-entry of the nitrous oxide solution into impregnator 406 in the event that the solution flow through conduit 105 is stopped while pumps 96 and 97 continue to run. Conduits 98 and 99 merge into a single conduit 105 at a position beyond the by-pass valves 100 and 101. Conduit 105 carrying the nitrous oxideimpregnated water under pressure is delivered to an underthe-cap filling machine of the type disclosed in Focht Patent 2,947,904.

In the process of packaging the product of Example I, a vacuum pump was connected to conduits 37 and 60 with valve 61 in open position. After a vacuum of 26 inches of mercury was established in the deaerator 23 and impregnator 46, water maintained at a temperautre of 70 F. by temperature control regulator was introduced into the vacuum deaerator 23 through conduit 21 and spray head 24. Valve 61 was closed and nitrous oxide maintained at a pressure of 250 p.s.i.g. by pressure control unit 73 was introduced into the top of impregnator 46.

After deaerated water accumulated in the vacuum deaerator 23 to a level between positions 31 and 32 and the nitrous oxide had reached a pressure of 125 p.s.i.g. in impregnator 46, pumps 43 and 44 were started and deaerated water pumped into impregnator 46 through conduit 45 and spray head 54. Addition of the water to the deaerator unit 23 increased the nitrous oxide pressure therein to 250 p.s.i.g. Nitrous oxide prevailing in the headspace of impregnator 46 became dissolved in the water as the water was sprayed through it. After several inches of water impregnated with nitrous oxide had accumulated in the bottom of impregnator 46, it was recycled through heat exchanger 78. This was accomplished by starting pump and 81 which pumped nitrous oxide impregnated water from the bottom of impregnator 4-6 through conduit 79 into heat exchanger 78 and back into impregnator 46 through conduit 84 and spray head 85. Recirculation of the nitrous oxide impregnated water served to maintain the temperature of the liquid in impregnator 46 at a temperature of 70 F. and to further expose the water in the form of a fine spray to additional compressed nitrous oxide in the head space of impregnator 46 thereby increasing and stabilizing the amount of nitrous oxide dissolved in the water. After approximately 1.9% by weight of nitrous oxide became dissolved in the water maintained at 70 F. under nitrous oxide pressure of 250 p.s.i.g., pumps 96 and 97 were started causing the nitrous oxide impregnated Water to flow from the bottom of impregnator 46 through conduits and 98 and 99 into conduit connected with under-the-cap filling machine of the type described in United States Patent 2,947,- 126 to Focht. There the measured amount of water impregnated with nitrous oxide was injected into each of the several containers as the final component of the spray wax, the formula of which is presented at the beginning of the example. The pressure of each of the containers filled in this manner was checked immediately after filling and found to have a gauge pressure of approximately 80 p.s.1.g.

The contents of several of the containers packaged in this manner were totally dispensed from the containers while observing the spray patterns. Excellent spray patterns were produced until the last of the liquid was dispensed from the containers. Although pressure within the containers dropped from about 70 p.s.i. to about 35 p.s.i. while the contents were being dispensed, no appreciable difference in spray pattern was observed.

In practicing the present invention for the pressure packaging of aqueous wax emulsions with a nitrous oxide propellant, nitrous oxide will be dissolved in the water which is added to the container as a second portion of the product in an amount ranging from about 0.5% to about 5% by weight of the Water in which it is dissolved. This may be accomplished by any desired technique such as bubbling the nitrous oxide through water by use of a sparger or by spraying the water through a nitrous oxide atmosphere under controlled temperature and pressure conditions as outlined above. When the spray method is used the temperature of the water and pressure of the nitrous oxide may be varied widely between about 35 F. and 200 F. and about 1 and about 50 atmospheres gauge respectively. More preferably, the water will be maintained at a temperature of between about 40 F. and about F. and the pressure of the nitrous oxide between about 5 and 35 atmospheres gauge. Narrow and more specifically preferred temperature and pressure ranges for dissolving nitrous oxide in water by the spray method are a water temperature of between about 60 F. and about 80 F. and a nitrous oxide pressure of between about 10 and about 25 atmospheres gauge. The above Example I falls into these very specific ranges.

The amount of water to be used in the first portion of the concentrate, which is deposited in the container prior to the addition of the final portion of water containing nitrous oxide, may vary from about 25% to about 75% by Weight of the total amount of water in the final emulsion in the package.

Additional examples will now be presented. to further exemplify the invention and indicate its value.

9 Example 11 An aqueous wax emulsion containing water, wax and an emulsifying agent in the following amounts was pressure packaged in 16 ounce cylindrical metal containers with nitrous oxide as the propellant in accordance with the present invention.

Percent by weight Microcrystalline wax 4.0 Sorbitan monolaurate (emulsifier) 1.5 Water 93.1

Nitrous oxide 1.4

In doing this, an aqueous wax emulsion was prepared with the above ingredients omitting the nitrous oxide and 70% of the water. This concentrated emulsion represented the first portion of the concentrate. Several 16 ounce metal containers were filled, each with 3.5 ounces of the concentrated emulsion and with 10.5 ounces of water saturated with nitrous oxide as in Example I also using an under the cap filler. These packages, like those of Example I, gave excellent spray patterns throughout the life of the container and the product functioned properly as a spray surface polish.

Example III An aqueous wax emulsion containing water, wax, emulsifier, petroleum distillate, and a silicone fluid in the following amounts was packaged in 8 ounce cylindrical metal containers with nitrous oxide as the propellant.

Percent by weight Microcrystalline wax 0.69 Dimethyl polysiloxane 2.66

Span (sorbitan monolaurate) and Tween 20 (polyoxyethylene sorbitan) in equal amounts (emulsifiers) .83 Mineral spirits 5.92 Water 88.30 37% formaldehyde .20 Nitrous oxide 1.40

The formaldehyde was added as a bactericide.

A concentrated aqueous wax emulsion was prepared in accordance with the above formula omitting the nitrous oxide and 68.7% of the Specified amount of water. Several 8-ounce cylindrical metal containers were filled, each with 1.75 ounces of this concentrated wax emulsion and thereafter with 5.25 ounces of water having nitrous oxide dissolved therein as outlined in Example I. The containers were filled with an under-the-capfiller of the type disclosed in United States Patent 2,947,126 issued to Focht.

These packages had a pressure of approximately 80 p.s.i.g. which dropped to about p.s.i.g. as the product was dispensed. All delivered excellent spray patterns as long as product remained to be dispensed. The product produced an excellent lustre to furniture when sprayed thereon and wiped dry. The product, an oil in water emulsion in the container, apparently reverses phases when it hits the surface being polished and part of the water evaporates thereby providing a wax polish with a fine balance of water surviving to amplify the luster of the coating.

Example IV Example III was repeated by (1) forming an emulsion of the wax, silicone, emulsifiers, mineral spirits, formaldehyde and 32.3% of the water, (2) dissolving nitrous oxide in the remainder of the Water in the same concentration as in Example III, (3) emulsifying the resulting aqueous nitrous oxide solution with the emulsion of (1) in a pressure vessel and (4) thereafter transferring 7 10 ounces of the final emulsion containing nitrous oxide to each of several 8 ounce cylindrical metal containers. This method will be recognized as vaguely related to the Boe method as discussed earlier. I

It is presented for purpose of comparison and differs from the method of the present invention by the formation of the total emulsified product including propellant outside the container from which it is to be dispensed, followed by the transfer of the product to the container under pressure.

The containers so packaged functioned as an inferior spray polish. The wax emulsion was adversely affected by the manipulative steps necessary to emulsify it with the nitrous oxide solution in the pressure vessel and its transfer to the containers from which it was dispensed.

Upon spraying, an erratic pattern was achieved apparently as a result of a partial gelling of the emulsion. Also, the products so packaged did not produce the fine lustre produced by the products of Example III. Phase reversal of the emulsion on the surface treated did not appear to occur.

Example V Example III was again repeated, for comparative purposes, this time by preparing an emulsion of all of the water, wax, emulsifier, mineral spirits, and dimethyl sili cone. This emulsion, while maintained at a temperature of 70 F., were then sprayed through nitrous oxide maintained under p.s.i.g. pressure for the purpose of impregnating the aqueous component of the emulsion with nitrous oxide. The emulsion gelled during preparation and spraying to the extent that it was rendered unsuitable for pressure packaging. Even if it were possible to suitably prepare the product in this manner, it would be more difi'lcult and time consuming to package since the entire product would have to be injected into the containers by the filling machine. Packaging according to the present invention permits the first portion of the concentrate to be deposited in certain containers while the second portion of concentrate, namely the remainder of the water, to which nitrous oxide has been added, is injected into other containers, already filled with the first portion of the concentrate.

It will be appreciated by those skilled in the pressure packaging of emulsions that changes can be made in the present invention without departing from its spirit. Having described the invention, what is claimed is:

1. A method of filling an aerosol container with an aqueous wax emulsion containing nitrous oxide propellant comprising: (a) introducing into said container said aqueous wax emulsion and (b) subsequently introducing into said container, under pressure, a mixture of water and nitrous oxide, containing up to about 5% by weight nitrous oxide.

2. A method according to claim 1 wherein the water nitrous oxide mixture is obtained by spraying water through a nitrous oxide atmosphere.

3. A method according to claim 2 wherein said water is sprayed at a temperature from about 35 F. to about 200 F. through nitrous oxide maintained under a pressure of from about 1 to about 50 atmospheres.

4. A method according to claim 2 wherein the nitrous oxide water mixture is obtained by spraying said water at a temperature from about 40 F. to about F. through nitrous oxide maintained under a pressure of from about 5 to about 35 atmospheres.

5. A method according to claim 2 wherein the nitrous oxide water mixture is obtained by spraying said water at a temperature from about 60 F. to about 80 F. through nitrous oxide maintained under a pressure of from about 10 to about 25 atmospheres.

6. A method according to claim 1 wherein the water of the mixture of water and nitrous oxide is deaerated.

7. A method according to claim 1 wherein said aqueous Wax emulsions contain from about 0.3% to about 10% by 1 1 weight wax, from about 0.3% to about 5% by weight emulsifier, and from about 85% to about 99.4% by weight water.

8. A method according to claim 1 wherein said aqueous wax emulsion contains from about 0.3% to about 6% by weight wax, from about 0.3% to about 4% by weight emulsifier, and from about 90% to about 99.4% by weight water.

9. A method according to claim 1 wherein said nitrous 5% by weight nitrous oxide.

References Cited by the Examiner UNITED ALEXANDER H. BRODMERKEL, Primary Examiner. oxide water mixture contains from about 0.5% to about 10 J. CARSON J. B EVANS Assistant Examiners 

1. A METHOD OF FILLING AN OEROSOL CONTAINER WITH AN AQUEOUS WAX EMULSION CONTAING NITROUS OXIDE PROPELLANT COMPRISING: (A) INTRODUCING INTO SAID CONTAINER SAID AQUEOUS WAX EMULSION AND (B) SUBSEQUENTLY INTRODUCING INTO SAID CONTAINER, UNDER PRESSURE, A MIXTURE OF WATER AND NITROUS OXIDE, CONTAINING UP TO ABOUT 5% BY WEIGHT NITROUS OXIDE. 